1. Field of the Invention
The present invention relates to an unbalance measuring apparatus for measuring the magnitude of an unbalance of a small rotating body 10.
2. Description of the Related Art
In a conventional roller-drive type unbalance measuring apparatus, as shown in FIG. 5, bearings for rotatably supporting a shaft 11 of a rotating body 10 are constituted by two rollers 12a, 12b which are supported on-a support portion 4 via ball bearings. Due to this, in measuring the magnitude of unbalance of the rotating body 10, which is large in size and heavy in weight, by applying a rotational force to the rotating body before a measurement and allowing the rotating body to continue to rotate by virtue of inertial force while measuring the magnitude of unbalance of the rotating body, even with the bearings constituted by the rollers 12a, 12b, the change in rotational speed of the rotating body remains small during the measurement, and the unbalance measurement can be implemented with high accuracy (refer to Japanese Patent Publication No. 3438333).
In the conventional roller-drive type unbalance measuring apparatus which uses the rollers for the bearings for supporting the shaft of the rotating body, however, with a small and light rotational body, the frictional force which acts between the rollers and the rotating body becomes larger than the inertial force, whereby the rotational speed of the rotating body, which is under measurement, decreases drastically, leading to a problem that the magnitude of unbalance of the rotating body cannot be measured.